Determination of molecular parameters of NR/PU block copolymers by transport studies

The equilibrium swelling experiments of block copolymers based on natural rubber (NR) as soft segment and polyurethane (PU) derived from toluene diisocyanate (TDI) and 1,3-butane diol (1,3-BDO) as hard segment were performed in various solvents. Block copolymers with different NCO/OH ratio, viz., from 1.26 to 1.96 were employed in this study. The crosslink densities are found to vary with the NCO/OH ratio employed in the synthesis of the samples. The sorption behaviour is also found to vary with the NCO/OH ratio. The equilibrium swelling experiments have been used to determine the molecular parameters such as molecular mass between crosslinks, crosslink density, polymer-solvent interaction parameter, etc. The equilibrium swelling values were also used to calculate the solubility parameter values of the block copolymers.